JPH02144550A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide durability against the generation of wear and flaws on the surface of the photosensitive body by rubbing and to obtain stable images having a high grade under high humidity by incorporating fluorine-contained resin powder into the surface layer of the photosensitive body and specifying the content of the inorg. ash incorporated into this layer. CONSTITUTION:The surface layer of the photosensitive body contains the fluorine-contained resin powder as a solid lubricating agent and the content of the inorg. ash incorporated into this layer is confined to <=0.1wt.% of the weight of the total solid content forming the layer. Namely, the fluorine- contained resin powder is uniformly dispersed as the solid lubricating agent into the layer furthest from the base and the content of the ash by the worn powder and splinters of the media for grinding to be incorporated into the fluorine-contained resin powder at the time of dispersing the powder is confined, by weight, to <=0.1wt.% of the weight of the total solid content of the layer in which the fluorine-contained resin powder is dispersed. The mechanical durability characteristics against the flaws, wear, etc., and the stability by an environmental change are improved. In this way and the images having the high grade are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more particularly to a highly durable electrophotographic photoreceptor having excellent mechanical strength, surface lubricity, temperature resistance, and imageability.

[Prior Art] An electrophotographic photoreceptor is required to have predetermined sensitivity, electrical properties, and optical properties depending on the electrophotographic process to which it is applied. In a photoreceptor, electrical and mechanical external forces such as corona charging, toner development, transfer to paper, and cleaning are directly applied to the surface layer of the photoreceptor, that is, the layer furthest from the support. Durability against them is required.

Specifically, durability is required against surface abrasion and scratches due to rubbing, and surface deterioration due to ozone generated during corona charging under high humidity.

On the other hand, there is also the problem of toner adhesion to the surface layer due to repeated toner development and cleaning, and to solve this problem, it is required to improve the cleaning properties of the surface layer.

Various methods have been proposed to achieve the characteristics required for the surface layer as described above.

As one of the methods, it is effective to provide a resin layer on the surface in which a solid lubricant of fluororesin powder is dispersed.

By providing a resin layer in which fluorine-containing resin powder is dispersed, durability against scratches, surface cleaning, and abrasion is improved, and the water repellency and mold releasability of the photoreceptor surface are improved under high humidity conditions. It is also effective in preventing surface deterioration.

In addition, when provided as a retainer on the surface, charge transporting materials and charge generating materials that are susceptible to deterioration by ozone are separated from the surface, further improving durability.

When dispersing this fluororesin powder into a resin, if the powder is mixed directly into the resin, it will not be completely uniformly dispersed, and the fluororesin powder itself will aggregate and contain many coarse particles. Because it is.

The coating film formed is non-uniform, and the coarse particles cause image defects such as pinholes and damage to the machine, such as blade breakage.

Therefore, when dispersing fluorine-containing resin powder into a resin, it is necessary to use some kind of mechanical pulverization means to reduce the particle size while dispersing.There are various methods of mechanical pulverization, but in this case A method that is also superior in terms of quantity is the pulverization method using shear stress of media such as poles or beads using a sand mill, ball mill, attritor, or red devil.

Other methods, such as roll mills, cannot make the gap between the rolls small enough to sufficiently crush coarse particles, and crushers such as homogenizers cannot provide a crushing effect on all coarse particles; It is unsuitable because it has the disadvantage that it cannot be completely crushed.

Now, if dispersion is carried out using a dispersion method suitable for fluororesin powder, such as the above-mentioned sand mill, the fluororesin powder will be pulverized and become small enough not to cause any problems.
Abrasion powder and debris from the media used for crushing become mixed in.

If a large amount of this wear powder and debris is mixed in, it will have a negative effect on the potential characteristics and image characteristics, and as the amount of wear powder increases, the dispersion stability of the dispersed fluororesin powder will be inhibited, resulting in agglomeration. Since coarse particles are produced and the coating film is non-uniform, it further deteriorates image characteristics and durability characteristics, as well as image characteristics and durability characteristics under high temperature and high humidity conditions.

[Problems to be Solved by the Invention] An object of the present invention is to provide an electrophotographic photoreceptor that has durability against surface abrasion and scratches caused by rubbing and eliminates the above-mentioned drawbacks. , To provide an electrophotographic photoreceptor that can stably produce high-quality images under high humidity, that does not accumulate residual potential in repeated electrophotographic processes, and that can always stably produce high-quality images without image defects such as pinholes. An object of the present invention is to provide an electrophotographic photoreceptor from which high-quality images can be obtained.

[Means for Solving the Problems, Effects] The present invention provides an electrophotographic photoreceptor having a photosensitive layer on a conductive support E, in which the surface layer of the photoreceptor contains fluorine-containing resin powder as a solid lubricant. .

The electrophotographic photoreceptor is characterized in that the amount of inorganic ash contained in this layer is 0.1% by weight or less of the total solid content forming the layer.

Specifically, in the electrophotographic photoreceptor of the present invention, fluorine-containing resin powder is uniformly dispersed as a solid lubricant in the layer (surface layer) farthest from the support, and.

When dispersing this fluororesin powder, the amount of ash due to abrasion powder and debris of the grinding media mixed in is determined by the weight ratio of the solid content in which the fluororesin powder is dispersed: 1! quantity 0
．． The content is 1% by weight or less.

Examples of the fluororesin powder used as a solid lubricant in the present invention include tetrafluoroethylene, trifluorochloroethylene, hexafluoroethylene propylene, vinyl fluoride,
Resin powders such as polymers such as vinylidene fluoride, difluoroethylene chloride, or trifluoropropylmethylsilane, or copolymers with vinyl chloride, or copolymers of tetrafluoroethylene and hexafluoropropylene are used as appropriate. In particular, tetrafluoroethylene resin, vinylidene fluoride resin, and copolymer of tetrafluoroethylene and hexafluoropropylene are preferred, and the molecular weight of the resin and the particle size of the powder can be selected as appropriate.

Furthermore, in the present invention, it is also effective to add small amounts of additives such as various surfactants, coupling agents, and leveling agents as dispersion aids in order to further increase the dispersion effect.

The content of the fluorine-containing resin powder to be dispersed is 1 to 50% by weight based on the weight of the total solid content of the contained layer,
In particular, 5 to 40% by weight is suitable.

The binder resin used for dispersion may be any polymer with film-forming properties, but polymethacrylate, polycarbonate, polyarylate,
Preferred are polyester, polysulfone, polystyrene, styrene-methacrylate copolymer, and the like.

In the present invention, in order to suppress the amount of ash mixed in during dispersion to 0.1% or less, it is necessary to set appropriate dispersion conditions.

The dispersion conditions to be considered regarding the dispersion method include the rotation speed, the amount of media, the size of the media, the ratio between the amount of media and the amount of dispersion liquid, or the feed amount of dispersion liquid.
The viscosity of the dispersion liquid, etc.

Furthermore, if this condition cannot be satisfied depending on the dispersion conditions, separation work under specific conditions is required to remove wear particles and the like.

When dispersing using a ball mill, if the rotation speed is lower than a certain rotation speed, the efficiency will be extremely low, so the coagulated coarse particles of the fluororesin powder will not be crushed, and if the rotation speed is high, the poles will separate. Because the impact of the collision between the pole and the wall is large, the amount of abrasion powder from the pole mixed in is large compared to the crushing effect on the fluororesin powder particles, and the particle size of the fluororesin powder is sufficiently small. The amount of abrasion powder exceeds the specified amount before it reaches the specified amount.

Furthermore, when pulverization is performed using a sand mill, a large amount of media abrasion powder and debris is mixed in.

A method such as centrifugation is generally used to remove this.

However, if the centrifugal minute number and machine rotation speed are too high, the dispersed particles of fluorine-containing resin powder will be removed together with the abrasion powder and debris, and if the centrifugation number is too low, the abrasion powder and debris will be removed. Cannot be removed.

Regarding the dispersion solution itself, if the viscosity of the solution is high, the grinding efficiency of ball mills and sand mills will decrease, and if the viscosity of the solution is extremely low, even if the conditions of the dispersion machine are set within an appropriate range, the grinding efficiency will be reduced. Abrasion powder and debris will be mixed in.

That is, when performing dispersion, the viscosity of the dispersion solution,
The produced electrophotographic photoreceptor exhibits good characteristics only when all of the dispersion conditions and the conditions for removing worn particles are within certain ranges.

The electrophotographic photoreceptor of the present invention is produced by dispersing fluorine-containing resin powder under the conditions shown below to reduce the ash content to 0.1% by weight or less of the total solid content forming the layer. It exhibits the good properties aimed at by the invention.

In the uninvention, the viscosity of the dispersion liquid in which the fluororesin powder is dispersed is 30 to 1,000 mPa, sec, especially Zoo
~500 mPa,see is appropriate.

When using a ball mill as a dispersion means, the number of revolutions is 1
-15Or,p,m, especially 10-60r,p,m are suitable.

Further, when a sand mill is used as the dispersion means, the circumferential speed of the disk is 3.7 to 22 m/see.

In particular, 7.3 to 15 m/sec is suitable.

Furthermore, when removing wear particles and debris using a centrifugal separator, a rotation speed of 1,000 to 7.00 Or, p, m, particularly 3,000 to 6.00 Or, p, 111 is appropriate. .

The electrophotographic photoreceptor of the present invention has a photosensitive layer on a conductive support. Although the photosensitive layer may take any known form, a functionally separated photosensitive layer in which a charge generation layer and a charge transport layer are laminated is particularly preferred.

The charge generation layer can be formed by coating a coating solution in which a charge generation substance is dispersed together with a binder resin in a suitable solvent on a conductive support by a known method.

The film thickness is, for example, 5. It is desirable to form a thin film layer with a thickness of preferably 0.1 to lpm.

Examples of charge-generating substances include pyrylium, thiapyrylium dyes, phthalocyanine pigments, anthoanthrone pigments,
Examples include dibenzpyrenequinone pigments, pyranthrone pigments, azo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanine, and quinocyanine.

The binder resin used in this case is selected from a wide range of insulating resins or organic photoconductive polymers, including polyvinyl butyral, polyvinylbenzal, polyarylate, polycarbonate, polyester, phenoxy resin, cellulose resin, acrylic resin, polyurethane. etc., and the amount used is preferably 80% in terms of content in the charge generation layer.
It is not more than 40% by weight, preferably not more than 40% by weight.

The solvent used is preferably selected from those that dissolve the resin described above but do not dissolve the charge transport layer or undercoat layer described below.

Specifically, ethers such as tetrahydrofuran and 1,4-dioxane, ketones such as cyclohexanone and methyl ethyl ketone, amides such as N,N-dimethylformamide, esters such as methyl acetate and ethyl acetate, toluene, xylene, Examples include aromatics such as chlorobenzene, alcohols such as methanol, ethanol, and 2-propanol, and aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichlorethylene.

The charge transport layer is laminated above or below the charge generation layer, and has the function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them.

The charge transport layer is formed by dissolving a charge transport material in a solvent together with a suitable binder resin as required and coating the layer, and the film thickness is generally 5 to 40 gm, preferably 15 to 30 gm.

Charge transporting substances include electron transporting substances and hole transporting substances. Examples of electron transporting substances include 2゜4,7-dolinitrofluorenone, 2,4,5゜7-titranitrofluorenone, chloranil, and tetranitrofluorenone. Examples include electron-withdrawing substances such as cyanoquinodimethane, and polymerization of these electron-withdrawing substances.

Hole-transporting substances include polycyclic aromatic compounds such as pyrene and anthracene, carbazole-based, indole-based, imidazole-based, oxazole-based, thiazole-based, oxadiazole-based, pyrazole-based pyrazoline-based, thiadiazole-based, triazole-based compounds, etc. heterocyclic compound, p-
Hydrazones such as diethylaminobenzaldehyde-N,N-diphenylhydrazone, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole
Compound, α-phenyl-4'-N, N-diphenylaminostilbene, 5-[4-(di-P-tolylamine)
benzylidene] -5H-dibenzo[a, d] A styryl compound such as cycloheptene, a benzidine compound, a triarylmethane compound, triphenylamine, or a polymer having a group consisting of these compounds in its main chain or side chain (e.g. poly-N-vinylcarbazole, polyvinylanthracene, etc.).

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can also be used.

Further, these charge transport materials can be used alone or in combination of 2 Mi or more.

When the charge transport material does not have film-forming properties, a suitable binder can be used. Specifically, insulating resins such as acrylic resins, polyarylates, polyesters, polycarbonates, polystyrene, acrylonitrile-styrene copolymers, polyacrylamides, polyamides, and #1 rubber, or organic resins such as poly-N-vinylcarbazole and polyvinylanthracene. Examples include photoconductive polyester.

As the conductive support on which the photosensitive layer is formed, for example, aluminum, aluminum alloy, stainless steel, titanium, nickel, etc. are used.

In addition, plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, etc.) or conductive particles (e.g., carbon black, silver particles, etc.) are coated with these metals or alloys using a suitable binder. It is possible to use plastic or a support coated on the conductive support with resin, or a support in which plastic or paper is impregnated with conductive particles.

A subbing layer having barrier and adhesive functions can also be provided between the conductive support and the photosensitive layer.

The subbing layer can be formed of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, aluminum oxide, or the like.

The thickness of the subbing layer is 5 ILm or less, preferably 0.1 part 3 m.

Another specific example of the present invention is an electrophotographic photoreceptor containing a charge generating substance and a charge transporting substance in the same layer. At this time, the charge transport material and the L-C boi IJ-N
L view,,ka,i2li,i2,1. Yu,.

Charge transfer complexes consisting of fluorenone can also be used.

Incidentally, a VI retaining layer can also be provided on the photosensitive layer.

The electrophotographic photoreceptor of this example can be formed by coating and drying a solution in which a charge generating substance and a charge transfer complex are dispersed in a suitable resin solution.

In the present invention, in order to form a layer in which the fluororesin powder is dispersed, it can be formed together with other main materials forming the core layer by, for example, a common coating method.

Hereinafter, the present invention will be explained in more detail in Examples.

[Example] Example 1 Polyamide (trade name Ami 570
A 5% methanol solution of M-8000 (manufactured by Tanishishi ■) was applied by dip coating to form a 1 gm thick subbing layer.

Next, 10 parts (parts by weight, the same applies hereinafter) of a disazo pigment having the following structural formula, 8 parts of polyvinyl butyral (trade name BX-L, manufactured by A-Sui Kagaku Kogyo ■), and 50 parts of cyclohexanone were mixed in a sand mill using 1 mm diameter glass beads. The mixture was dispersed for 20 hours.

70 to 120 parts (appropriately) of methyl ethyl ketone was added to this dispersion and coated on the undercoat layer to form a charge generating layer having a thickness of 0.15 parts m.

Next, 10 parts of polymethyl methacrylate, 5 parts of polytetrafluoroethylene powder (trade name Lublon L-2, manufactured by Daikin Corporation) as a fluororesin powder, 40 parts of chlorobenzene,
Hydrazone as a charge transport substance was mixed with 15 parts of tetrahydrofuran, placed in an alumina ball mill with alumina pole, and dispersed for 10 hours, 50 hours, 60 hours, 70 hours, and 100 hours. 10 parts of each compound were dissolved.

This solution was coated on the previously formed charge generation layer and heated to 100°C.
The electrophotographic photoreceptors thus prepared were designated as Samples 1, 2.3.4, and 5, respectively.

For comparison, an electrophotographic photoreceptor was prepared in the same manner except for using a solution without adding polytetrafluoroethylene, and Sample 6 was prepared.
shall be.

These samples were subjected to an electrophotographic process consisting of -5.5KV corona charging, image exposure, dry toner development, toner transfer to plain paper, and cleaning with a urethane rubber blade, and io and ooo images were passed through the paper. We conducted a durability evaluation.

Furthermore, the ash content in each coating solution was also measured.

Image 0.08 Same as above 0.10 Same as above 0.11 Pinhole occurrence Ground fog on white area Lightning 1 1 #L m 2 1 μm 3 1gm 4 1 JLm 5 1 Lum 6 5 Zenm In samples 1 to 3 The amount of wear on the surface of the electrophotographic photoreceptor was small, and both the potential and the image were stable.

In Samples 4 and 5, the amount of wear on the surface of the electrophotographic photoreceptor was small, but it is thought that pinholes were generated because the amount of abrasion powder, debris, etc. of the alumina balls increased. Regarding sample 5, the characteristics further deteriorated and soil blurring occurred due to an increase in bright area potential.

In sample 6, it is thought that the decrease in film thickness due to surface friction led to an increase in the bright area potential, which caused soil burr.

That is, it can be seen that when the ash content exceeds 0.1% by weight, the image characteristics are affected.

Example 2 An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that polyvinylidene fluoride powder was used in place of the polytetratetraethylene diethylene, and the same evaluation was performed.

As a result, as in Example 1, the amount of inorganic ash was 0.1
With the photoreceptor containing less than 1% by weight, uniform and stable images were obtained up to io and oooo sheets.

On the other hand, in the case of photoreceptors containing more than 0.1% by weight, image defects such as pinholes and ground blurring were observed.

Example 3 An aluminum cylinder of 80 φ x 350 mm was used as a conductive support, and a 5% methanol solution of polyamide (described above) was dip-coated onto this to provide a subbing layer with a thickness of lpLm.

Next, 1 part of aluminum chloride phthalocyanine, 10 parts of bisphenol Z type polycarbonate (manufactured by Mitsubishi Gas Chemical), 45 parts of cyclohexanone, and 1 part of dichloromethane were added.
Add 4 parts of polytetrafluoroethylene powder to the mixed solution containing 5 parts of polytetrafluoroethylene powder, put this mixed solution into a sand mill using 1 mm diameter glass beads as a media, and set the disc rotation speed to 2.0.
6 parts of a hydrazone compound having the following structural formula was dissolved in the solution recovered after dispersion for 50 hours at 0 Or, p, m.

The dispersion thus prepared was subjected to removal of worn particles of glass beads using a centrifuge #i machine under the following conditions, and then the amount of ash in the solid content was measured under each condition.

Show the results.

No centrifugation 2 minutes 5 minutes 10 minutes 15 minutes 20 minutes ■ 30 minutes 0.01 Next, sample solutions ■ to ■ are dip-coated onto the undercoat layer, and 19
A photosensitive layer with a thickness of μm was provided.

The electrophotographic photoreceptors thus prepared were designated as Samples 7 to 13 in the order corresponding to the sample liquids.

Samples 7 to 13 were installed in an electrophotographic copying machine that has -5,5KV co-charging, image exposure, dry toner development, transfer to plain paper, and cleaning steps with a urethane rubber blade, and heated at 23°C 155%. 50.000 at RH
A durability test was conducted on the sheets.

Show the results.

Ground strength pre-occurrence in white area 8 Same as above
1 lm9 Image defect caused by pinhole IJ
Lm Ground burr occurrence on the white background Same as above Uniform and stable image up to 50,000 sheets Same as above l Extension m 1 lm l lm 13 Same as above 2 lm In samples 7 to 10, glass bead abrasion powder and debris were mixed. This is thought to have caused pinholes and soil burrs, and sample 1, in which the amount of glass bead abrasion powder and debris was kept to 0.1% by weight or less by centrifugation.
Good results were obtained for Nos. 1 to 13.

For comparison, an electrophotographic photoreceptor was prepared in the same manner except without using polytetrafluoroethylene, and the same test was conducted. A good image could not be obtained due to soil blur due to the increase in potential.

[Effects of the Invention] The electrophotographic photoreceptor of the present invention has excellent mechanical durability against scratches and abrasion, stability against environmental changes, etc., and has remarkable effects on prevention of deterioration and stability of electrophotographic properties.

Claims (1)

[Claims] 1. In an electrophotographic photoreceptor having a photosensitive layer on a conductive support, the surface layer of the photoreceptor contains fluorine-containing resin powder as a solid lubricant, and inorganic ash contained in this layer. An electrophotographic photoreceptor characterized in that the amount of is 0.1% by weight or less based on the total weight of solids forming the layer.